The railroad industry has found that a substantial cost savings can be realized by eliminating the caboose from the end of freight trains. Thus, with the advent of the revenue operations of cabooseless freight trains, there arose the need for some type of telemetry equipment which was capable of sensing and monitoring the brake line pressure and also which is capable of determining the direction of motion and confirming the presence of the last car. In actual practice, the telemetry equipment includes the electronics circuitry, the radio transmitter, the pressure transducer, and the batteries which are all housed within an appropriate protective casing. It has been found that the most practical location for mounting the telemetry equipment is on the coupler of the last railway car since the "glad-hand" of the end of or rear coupling hose is readily available for measuring the brake line pressure. In addition, the last coupler location is obviously the end-of-train, and the body of the last car provides some protection against the elements and environment. However, the shape and bulkiness of the railroad car couplers makes it difficult to suitably mount the end-of-train equipment casing. Further, the equipment is exposed to the extreme shock and vibrations of the railroading milieu. Moreover, the equipment is repeatedly mounted and removed from the railroad cars and, accordingly, it is necessary to provide a method of quickly and easily attaching and detaching the end-of-train apparatus. While previous coupler mounting arrangements, one of which is shown and disclosed in U.S. Patent Application Ser. No. 593,778, filed Mar. 27, 1984, of Blosnick et al, entitled "Clamp for Railroad Car Coupler," have been proposed and used in mounting apparatus to the coupler of the last vehicle of a railroad train, many of these prior art apparatus supporting devices usually had one or more of the following shortcomings. In many cases, they were massive and bulky in size, difficult to mount and remove, unstable in use, expensive to manufacture, complicated in construction, and included an excess number of moving parts which were susceptible to undue wear and subject to ice freezing. In some cases, the coupler mounting arrangement did not permit the coupling of a helper locomotive in pusher operations in mountainous regions or in humping operations in classification yards or the coupling of other freight cars without the need of removing the end of train equipment from the coupler.